Finally, AHA's coronary calcium and CT statement sees the light of day

Shelley Wood

October 05, 2006

October 5, 2006 (Dallas, TX) - Exactly two years after Circulation editors announced that they would not, after all, be publishing an AHA writing committee statement on coronary artery calcium (CAC), the document has quietly appeared, somewhat ironically, as a "rapid access" publication online in Circulation [1 ]. In the much-anticipated statement, the writing group's conclusions represent something of a sea change, given the AHA's established hesitancy in supporting the technology.

"Coronary-artery calcified plaque, as determined by cardiac CT, documents the presence of coronary atherosclerosis, identifies individuals at elevated risk for myocardial infarction (MI) and CVD death, and adds significant predictive ability to the Framingham Score," the AHA's writing group concluded. According to lead author on the statement, Dr Matthew Budoff (Harbor-UCLA Medical Center, Torrance, CA), the statement was rewritten from scratch and underwent extensive peer review as a new document.

Back in October 2004, Circulation editor Dr Joseph Loscalzo yanked the planned publication after the Wall Street Journal and other news outlets apparently broke a journal embargo suggesting that the AHA had changed its position on CAC scanning. At the time, members of the writing committee denied leaking any aspects of the statement and told heartwire that they "respectfully disagreed" with the editorial decision after all the hard work they'd put in. Media outlets, including, had also reported the controversy over the only previous AHA/ACC expert consensus document in 2000 on electron-beam computed tomography (EBCT) for calcium scoring, in which one member of the writing group resigned and dissension persisted within the group even as the document was published [ 2 ].

A more peaceful process

This time around, according to writing group member Dr Roger Blumenthal (John Hopkins School of Medicine, Baltimore, MD), there was "very good consensus among the different authors even though we were from diverse backgrounds. Dr Budoff was an excellent leader and kept the project moving forward."

The two-year delay, Blumenthal adds, was due in part to a decision to include CT angiography as well as updated noncontrast/CAC literature but also to the need to reach consensus with the reviewers, whom he described as "cautious."

"Many of us think that the recommendations are on the conservative side, but that just means we need to develop more good research to show that the indications for selective use of cardiac CT really should be expanded," he told heartwire .

Budoff agreed. "Our conclusions are very definitive that this is a test that's going to be useful in clinical practice. The AHA is very conservative, by necessity: if they make a widespread recommendation that every American should get a calcium score, that has incredible implications for insurance companies and healthcare costs. So we have to take small steps here toward the end goal, but I think the science has really come along very strongly from the paper in 2000."

According to Blumenthal, consensus in the group and with the reviewers was helped by the fact that the divisive effect of direct-to-consumer advertising of CAC testing by manufacturers--which only hampered scientific evaluation of the imaging technique--has been removed from the equation. "The controversy about EBCT and [multidetector computed tomography] MDCT has faded away, since General Electric no longer is producing new EBCT scanners, only MDCT scanners," Blumenthal told heartwire . As well, while an EBCT test back in 2000 hovered around the $400 mark, a high-quality test today can be obtained for around $100.

A role for calcium tests in 2006

In the AHA/ACC EBCT statement published in 2000, the writing group concluded that EBCT testing for CAC was not superior to alternative noninvasive imaging techniques at diagnosing CAD and therefore could not be recommended for this purpose. The group also concluded that published literature could not answer the question of whether calcium scoring was additive to the Framingham score or National Cholesterol Education Program (NCEP) definitions in identifying asymptomatic patients at increased risk of coronary events. "In the setting of this degree of uncertainty, EBCT screening should not be made available to the general public without a physician’s request," the 2000 document concluded.

Now, in a document that draws heavily on studies published within the past two years and even within the past 12 months, the new AHA statement concludes, "The majority of published studies have reported that the total amount of coronary calcium (usually expressed as the 'Agatston score') predicts coronary disease events beyond standard risk factors. . . . These studies demonstrate that coronary artery calcified plaque is both independent of and incremental with respect to traditional risk factors in the prediction of cardiac events."

The most important guidance provided in the new document is, as expected, in intermediate-risk patients. As other statements have concluded, patients at the lowest and highest risk do not benefit from CAC screening: "Asymptomatic persons should be assessed for their cardiovascular risk with such tools as the Framingham Risk Score," Budoff et al's 2006 statement concludes. "Individuals found to be at low risk (<10% 10-year risk) or at high risk (>20% 10-year risk) do not benefit from coronary calcium assessment (class III, level of evidence: B)."

The document goes on to state that "in clinically selected, intermediate-risk patients, it may be reasonable to measure the atherosclerosis burden using EBCT or MDCT to refine clinical risk prediction and to select patients for more aggressive target values for lipid-lowering therapies (class IIb, level of evidence: B)." Of note, the document also supports as "reasonable" the use of coronary calcium assessment in the setting of equivocal treadmill or functional testing, or in symptomatic patients to determine cause of cardiomyopathy, or in patients with chest pain with equivocal or normal ECGs and negative cardiac enzyme studies (all class IIb, level of evidence: B)

Although there is no evidence of it in the published statement, the writing group and reviewers, in some cases, were at odds over the "b" designation given to many indications, suggesting that usefulness/efficacy is less well-established by evidence/opinion, as opposed to "a," meaning that the weight of opinion/evidence favors usefulness/efficacy, Blumenthal told heartwire .

"This is a great summary of the existing data," he emphasized. However, "a number of these indications throughout the paper were downgraded to class IIb, which was really just a compromise with one or two of the reviewers. . . . If you polled the individual writing committee members, most of these recommendations we felt should be class IIa, but I think it really doesn't make that much difference, quite frankly."

Minor quibbles

Even the definition of "intermediate risk" used in the statement is a minor point of contention.
"Right now, the message that comes across repeatedly is that this test may be useful in the intermediate-risk patient using the AHA criteria of a 10% to 20% 10-year risk, but many of us would probably prefer the ACC definition [of 'intermediate'] as a 6% to 20% 10-year risk, and that's what we put in the Bethesda conference on atherosclerosis imaging a few years ago," Blumenthal stated.

Giving an example, Budoff pointed out that an "intermediate-risk" definition of 10% to 20% 10-year risk tends to miscategorize women, who often underestimate their risk factors and face higher CVD risk within the 6%-to-10% range. "I kind of like the broader definition of 6% to 20% because if we're too strict in these guidelines, most women fall out of the risk assessment." In fact, Budoff adds, calcium scores may be even more appropriate in women than in men, who tend to have more clear-cut risk-factor profiles.

"It's appropriate from the AHA's point of view to be on the cautious side: we clearly are facing increasing medical costs as our population gets older, and it's incumbent on all of us in the academic community to try to prove what areas new technology can be helpful in targeting the right patient and other areas where we may be able to save money in terms of medication costs," Blumenthal said.

Indeed, management of intermediate-risk patients will continue to spark debate. Some clinicians may feel a CAC test is unnecessary given recent recommendations, based on the ASCOT trial, that patients with a 10% to 20% 10-year risk should have an optimal LDL-C target of less than 100, Blumenthal said.

"A lot of people will read this document and say, well, it says we can use this CAC scan in the intermediate-risk range, but on the other hand I have some guidance from the latest update to NCEP and I might as well just treat the patients if they get to that 10% 10-year risk."

Budoff, however, argues that ASCOT patients, who had hypertension plus three additional risk factors, were not, in fact, in the "intermediate-risk" group but were high or intermediate-high risk. "What this document is saying is that if you have a patient with one risk factor, in that gray zone, a calcium score may make you much more dogmatic about therapy and perhaps in your choice of level of therapy."

Someone with a calcium score over 100, Budoff clarified, faces an increased risk of cardiovascular events--as much as 2% per year. In these patients, he said, "I'm more dogmatic about therapy, patients are more compliant, and it gets me motivated to treat them more aggressively, whereas with a calcium score of zero I am less motivated to treat and less concerned about cardiovascular events, at least in the next three to five years."

CT screening in practice

Many physicians may not be aware of the sheer extent of the literature, Blumenthal noted, and this may give them pause for thought. "There are clearly going to be some people who are going to read the document and say, there really are more data out there then I had realized, and I have an 'intermediate-risk' patient--especially one who may not be inclined to go on lifelong aspirin and cholesterol-lowering medicine--for whom there is a large body of evidence that suggests that knowing the calcium score would help effect management."

That said, the test shouldn't be used if it's not going to influence practice, he adds. "The key is, people need to know what they're going to do with the results. It's pretty easy to say that if you're already committed to putting someone on aspirin and lipid-lowering therapy that you really don't need this test, but if you're on the fence or the patient is on the fence, then this document does a really nice job of summarizing the strengths and limitations of the existing data."

Overall, Blumenthal concluded, he and the rest of the writing group are "happy with the way it came out."

Ultimately, like all consensus documents, the statement will inevitably be interpreted subjectively. "I think people who are more favorably inclined to consider the test for the intermediate-risk patient will find this document supports their view," Blumenthal said. "And those who feel that we need a higher standard than what we currently have will also feel comfortable with the lower classification level of class IIb."

Answers to some of the outstanding questions that lead to the "b" designation may not be out for several years, although experts are pinning their hopes on the Multi-Ethnic Study of Atherosclerosis (MESA) study, the Heinz Nixdorf RECALL study, and the Dallas Heart Study to better clarify the role of CT imaging in risk prediction and management. "These are at least a couple of years away, and whether or not there will be enough events to answer some of these key questions remains to be seen," Blumenthal said.

An ACC statement on CT is also currently under peer review and expected out in the coming months.

A nod to MDCT and CT angiography

While the bulk of the statement focuses on noncontrast CT--used primarily for CAC screening--a smaller section of the statement addresses the use of CT angiography using MDCT or EBCT. The use of either modality to evaluate noncalcified plaque or to track atherosclerosis or stenosis over time is "not recommended" (class III, level of evidence: C), the document notes. However, the statement does conclude that CT coronary angiography is "reasonable for the assessment of obstructive disease in symptomatic patients (class IIa, level of evidence: B), while use of CT angiography in asymptomatic patients as a screening test is not recommended, nor is the technology recommended to assess outcomes after stent placement (for both: class III, level of evidence: C). Use of CT angiography for CABG follow-up or for assessment of anomalous coronary arteries is also discussed, but both are given a "C" level of evidence.

  1. Budoff MJ, Achenbach S, Blumenthal RS, et al. Assessment of coronary artery disease by cardiac computed tomography, a scientific statement from the American Heart Association Committee on Cardiovascular Imaging and Intervention, Council on Cardiovascular Radiology and Intervention, and Committee on Cardiac Imaging, Council on Clinical Cardiology. Circulation 2006; DOI: 10.1161/CIRCULATIONAHA.106.178458. Available at: .

  2. O’Rourke RA, Brundage BH, Froelicher VF, et al. American College of Cardiology/American Heart Association expert consensus document on electron-beam computed tomography for the diagnosis and prognosis of coronary artery disease. Circulation 2000; 102:126-140.

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